Gas turbine engines are mounted on an aircraft by a support structure such as a pylon. A nacelle encloses the engine forming an enclose shelter which is aerodynamically contoured to reduce drag during aircraft operations. The nacelle usually is supported in part from the pylon and in part from the engine.
This nacelle has a removable metal and or composite covering known as a cowling. The cowling includes a fan duct reverser or outer cowl and a core or inner cowl. Each of the cowlings has a pair of clam shell doors hinged at the top. Each door may then be opened to provide access to service the engine.
The larger diameter outer cowling and the smaller diameter inner cowling have in the past often been axially split. Accordingly, hinge lines could be placed on the top of each cowling for opening the clam shell doors.
Recently, however, designs have been used with the inner cowling having the front end attached at the inside of the outer cowling and being supported therefrom. This provided additional stiffness for the nacelle and permitted the inner nacelle to bear against the engine and share loads. This limited the bending of the engine reducing distortion of the casing and rubbing of the blades. It follows that the two cowlings must be open together around a hinge line established by the outer cowling. The inner cowling then rotates around a hinge point which is not located on the cowling itself.
The inner cowling door must be tightly secured against the engine after being closed in order to provide the desired amount of load sharing. One way is to attach the doors at the top to the support structure while also latching the two doors together at the bottom. A top mounted latch is difficult to reach by people on the ground because of the size and location of present day aircraft engines. Some alternate designs have evolved, with these also latching in an upper quadrant. These all have the same difficulty of access. Planes have flown with the cowl latches not being closed because of the inability to reach or see that these latches are engaged. This results in excessive deflection of the engine and rubbing of the blades, thereby reducing performance efficiency and shortening the engine life.
U.S. Pat. No. 4,549,708 introduces a cable arrangement operable from the bottom of the cowling, remotely actualing latching and unlatching to the support structure. A cable located within the surrounding cowling is used to maintain engagement of the latch and the tensile load. When load is released on this cable a spring within the latch mechanism disengages the latch from the support structure. The latch therefore is free to ride with the cowling as the clam shell doors open. On closure the latch is placed adjacent the pin to be grabbed and closed as tension is placed on the cable.
Implementation of the arrangement has not been fruitful because the cable must be lubricated and it binds as the lubricant cokes up. A guide within the hat section is required because of the inability of the cable to take any compressive load. The arrangement depends on a spring to unlatch and has the potential of hanging up at a time when it is desired to open the door. It also has a limited load capability.